Bug in mmap()

[Bruce Korb <bkorb at gnu dot org>]

Hi all,

An issue in my code reveals a bug in mmap():
/lib/libc.so.6.1 Linux/alpha 2.6.13.2

> My mapping descriptor structure shows this:
>
> (gdb) print *pMI
> $2 = {txt_data = 0x2000001c000, txt_size = 8192, txt_full_size = 16384,
>  txt_fd = 7, txt_zero_fd = -1, txt_errno = 0, txt_prot = 0, txt_flags = 0,
>  txt_alloc = 0}
>
> Immediately before this call:
>
>        pNuls = mmap(
>                (void*)(((char*)pMI->txt_data) + pMI->txt_size),
>                pgsz,
>                PROT_READ|PROT_WRITE,
>                MAP_ANONYMOUS|MAP_FIXED|MAP_SHARED, 0, 0 );
>
> The address passed is:
>
> (gdb) print 0x2000001c000+8192
> $5 = 0x2000001e000
>
> It seg faults instead of returning ((void*)-1).
So, the "|MAP_SHARED" dinkleberry is left over from the copied text
where I am mapping a real file.  Anyway, his call should either work
or return ((void*)-1).  Not seg fault.  Handling a seg fault is
painful.  This could be a kernel issue, of course, but libc is
between my code and there, so I am reporting it to you....Thanks - Bruce